Auxiliary data for controlling a satellite

Abstract

The present disclosure relates to a method of generating auxiliary data for controlling a satellite travelling in orbit around Earth, the method comprising: receiving tracking data for the satellite; applying an orbit determination algorithm including: estimating an orbit for the satellite based on the tracking data; and predicting, based on the estimated orbit, future ephemerides data of the satellite; generating auxiliary data comprising predicted future ephemerides data; and transmitting the auxiliary data to the satellite for use in the satellite's attitude and orbit control.

What is claimed is: 
     
       1. A method of generating auxiliary data for controlling a satellite travelling in orbit around Earth, the method comprising:
 receiving tracking data for the satellite; 
 applying an orbit determination algorithm including:
 estimating an orbit for the satellite based on the tracking data, and predicting, based on the estimated orbit, future ephemerides data of the satellite; 
 
 generating auxiliary data comprising predicted future ephemerides data; 
 transmitting the auxiliary data to the satellite for use in control of an attitude and an orbit of the satellite; and 
 determining a current position of the satellite based on the predicted future ephemerides data comprised in the auxiliary data when GNSS or GPS sensor data on board the satellite is not available or not reliable, and using the current position to control the satellite's attitude and orbit, 
 wherein at least the applying the orbit determination algorithm and the generating the auxiliary data are performed ground-based. 
 
     
     
       2. The method as claimed in  claim 1 , wherein the tracking data comprises Global Navigation Satellite System ‘GNSS’ sensor data, satellite laser ranging ‘SLR’ measurements or radar measurements of the satellite. 
     
     
       3. The method as in  claim 1 , wherein the tracking data is indicative of a series of time and corresponding position and velocity of the satellite. 
     
     
       4. The method as claimed in  claim 1 , wherein estimating the orbit for the satellite is further based on a previously estimated orbit. 
     
     
       5. The method as claimed in  claim 1 , wherein the tracking data corresponds to a predetermined time interval, optionally corresponding to the time between two ground station passes of the satellite. 
     
     
       6. The method as claimed in  claim 5 , wherein the tracking data comprises one or more gap(s) corresponding to one or more tracking outage(s) during the predetermined time interval. 
     
     
       7. The method as claimed in  claim 1 , wherein the method is repeated at every pass of the satellite, such that tracking data is received per pass of the satellite and the generated auxiliary data is transmitted per consecutive pass of the satellite. 
     
     
       8. The method as claimed in  claim 1 , wherein the method is repeated in parallel for a plurality of satellites. 
     
     
       9. The method as claimed in  claim 1 , wherein the auxiliary data comprises predicted futures ephemerides in temporal intervals of up to a maximum interval equal to one of one minute, two minutes, and 5 minutes, spanning over a time period that is less than or equal to 6 hours, 12 hours, or 24 hours. 
     
     
       10. The method as claimed in  claim 1 , wherein the auxiliary data comprises predicted future ephemerides covering at least one orbital period of the satellite. 
     
     
       11. The method as claimed in  claim 1 , wherein estimating the orbit includes filtering the tracking data to provide filtered ephemerides of the satellite. 
     
     
       12. The method as claimed in  claim 11 , wherein predicting future ephemerides data of the satellite includes a propagation forward in time from the filtered ephemerides. 
     
     
       13. A ground segment for generating auxiliary data for controlling a satellite travelling in orbit around Earth, wherein the ground segment is configured to perform the method of  claim 1 . 
     
     
       14. A ground segment for generating auxiliary data for controlling a satellite travelling in orbit around Earth, the ground segment comprising:
 a receiving module configured to receive tracking data for the satellite; 
 an orbit determination tool kit ‘ODTK’ configured to apply an orbit determination algorithm including: estimating an orbit for the satellite based on the tracking data, and predicting, based on the estimated orbit, future ephemerides data of the satellite; 
 an auxiliary data module configured to generate auxiliary data comprising predicted future ephemerides data; and 
 a transmitting module configured to transmit the auxiliary data to the satellite for use by an attitude determination and control systems ‘ADCS’ unit of the satellite, to determine a current position of the satellite based on the predicted future ephemerides data comprised in the auxiliary data when GNSS or GPS sensor data on board the satellite is not available or not reliable, and using the current position to control the satellite's attitude and orbit, 
 herein at least the applying the orbit determination algorithm and the generating the auxiliary data are performed ground-based. 
 
     
     
       15. The ground segment of  claim 14 , wherein components of the ground segment are distributed over multiple locations. 
     
     
       16. Use of the ground segment as claimed in  claim 14  for generating auxiliary data to control one or more satellite(s) travelling in orbit around Earth, wherein each of the one or more satellite(s) is configured to determine its position based on the auxiliary data. 
     
     
       17. A satellite for travelling in orbit around Earth, the satellite comprising:
 a receiving module configured to receive auxiliary data generated for the satellite according to the method of  claim 1 ; and 
 an attitude determination and control systems ‘ADCS’ unit for controlling the satellite in orbit, 
 wherein the ADCS unit is configured to determine a current position of the satellite based on the auxiliary data. 
 
     
     
       18. The satellite of  claim 17 , further comprising:
 an on-board computer, wherein the on-board computer is configured to select a latest predicted ephemerides data from the auxiliary data based a current on-board time of the satellite, and 
 an orbit propagator forming part of the ADCS unit configured to numerically propagate the selected predicted ephemerides data based on the current on-board time to determine a current position of the satellite. 
 
     
     
       19. The satellite of  claim 17 , the satellite further comprising a tracking module for tracking the satellite, wherein
 the tracking module is a GPS sensor module, 
 wherein the ADCS unit is further configured to determine a current position of the satellite based on sensor data of the tracking module, wherein and 
 the ADCS unit is configured to switch from the sensor data to the auxiliary data if the tracking module is non-functional. 
 
     
     
       20. The satellite of  claim 17 , wherein the satellite is a microsatellite and/or a radar satellite for earth observation.